Electric hammer



Dec. 3, 1940- P. A. MACCHIONI ELECTRIC HAMMER Filed Dec. 27, 1938 Patentefi Dec. 3, 1940 UNETED STATES ELEeTRIo HAMMER Pietro Aurelio Macchioni, Turin, Italy, assignor to See. An. S E. M. B. I Turin, Italy Applicationflecemher 27 1 Claim,

This invention relates to reciprocating electric hammers of the type comprising a solenoid en closed in. casing of magnetic material and e movable care to which is imparted a reciprocating motion by the magnetic pull and reaction of an opposir 7 spring.

An object "this invention is te provide electr c of the type referred to above, in which the magnetic casing is constituted, by sheet metal punchirlgs radielly arranged about the hairline; axis so as to form a. cage enclosing the coil. The outer edges of the punchings are curved to e, rel form to interlock one an other, anal the machines are clamped between two enel plates h means of bolts exterzo through th or With this arrange ht emetic paths f0 meal,

' the internal ham" 7 by reason er the large oi the easing.

- inventz n with. the concavity g the concavity l e so as be eh bolts damping the ste l end eectlori on er erlletr eel. swing, ("Zehetes coil an annular cage termed 13; arranged and em'vee form a channel. E te steehihg'e a, ii, 0 er smel -shaped pertions 3, 2 a errengecl i th the coneevlty of one eteeiring inverted with re spent to the el hele e13 adjacent steelzings so es w to form at 1338, Serial No. 247,962

conduits 5, that are utilized as passages for the bolts 6 clamping the cage between the end plates l and a, respectively.

It will be apparent that with this. arrangement a strong magnetic shell is obtained, uhefieeteei by the strong vibrations to which the ier is subjected in operation The shell has fitted therein at one a ter-core 9 provided with e flange of which it rests on the punchinge, an axial bore enlarged at one end for the disc l l ehuttec by a, powerful lined on its remaining portien by serving as a guide for e shaft i l eon l oteei movable core l5 having at its opposite e111? extension guided in its axial moi bushing ll integral with the lm'o the plate The movable core iii rests on alet-e e seated in an annular recess t1 adapted to absorb shocks, eveidhg thereof to the shell. With the above deseriberi movable core is guicied in its me ends by means of the shaft to a 25 safely avoiding any frict and the spoel eml unclue weer Both the eounter oore and formed by radially arranged on netic metal, tightly clempeel to at their ends to clamping rings sioie the magnetic field compact civ l I proof b-lOClZS. This construction em he cluces losses eddy currents.

The spool ls resiliently seating by means of i in the inner recesses 0,0, having Slli&lli2'i$li1&tl therein, and held against the star. UL the plate The plates l ti ere proviel 01- the punching-e anal on its out a flange forming a box, en leting disc carrying a l e plate connected to one of the in cable is provided with e eon ing with the contact of the static ing the spring l2.

bolt :1 provided with a winged nut forclamping the cover 3| on the plate I. The cover has centrally screwed therein an adjusting plug 34 for the spring I! and a button 35 is arranged in a branch of the handle. The button 35 acts through the spring 38 and the push-rod 31 to move the plate 25 into engagement with the plate 26 so as to close the circuit energising the coil.

Use of the hammer is extremely simple. The cable is connected to an alternating current source and the tool 38 is fitted into the hub l8,

whereupon the button 35 is depressed, thereby ,closing the circuit energising the coil 1.

.The movable core I5 is normally held by the spring i2 against the shank of the tool. As the coil is energised the core is drawn inwardly, compress- In passing from a positive to a negative alternation and vice versa the current drops to zero and the spring I? violently pushes the core outwardly thereby imparting a blow to the tool.

The core strikes in a minute a number of blows equal to the number of alternations of the current. By adjusting the resilient reaction of the big spring I2 or of the shock absorbing spring IS, the effect of blow may be reduced.

In operation the extension Ii on the movable core acts as a piston and generates air currents which, by flowing along the movable core and filtering between the spool and core and counter- I core and between the punchings ofthe shell, efliclently cools the inner parts of the hammer. The dissipation of heat is further improved by the form and arrangement of the punchings of the shell.

What I claim is:

An electric hammer comprising, end plates, a magnetic shell arranged between said end plates and constituted by punchings radially arranged about the hammer axis and curved to a channel form near their outer edge, said punchings being grouped to form stackings with the channelshaped portions in interlocking engagement, said stackings being arranged in such manner that the concavity of the channels oi a stacking is inverted with respect to the concavity of the channels of adjacent stackin'gs so as to form longitudinal conduits in proximity to the outer periphery alternating with longitudinal recesses in proximity to the, inner periphery of the shell, an energizing coil seated in an annulargroove formed in the inside face of said shell, spring means in said recesses pressed between said coil and one of the end plates to oppose the vibrations of the coil, and bolts in said conduits to clamp the shell between said end plates and form a rigid vibration resisting unit.

PIETRO AURELIO MACCHIONI. 

